Finding an object's location/scale with values set to zero?
If the location and rotation values of an object are set to 0, and scale values are set to 1, it means that it has its location, rotation and scale either set to default or applied (scale zero would make it compressed to a single point). As far as I know, there is no way to retrieve the original values (unless undo apply transformations immediately, without saving and closing). 

There's a possibility to estimate the original location: applying location makes x = y = z = 0 but it means the object's pivot is at (0, 0, 0) - so you can temporarily use "set origin to geometry" to get its actual position, in a sense.

Here an example starting situation:



After using the command set origin to geometry:



You get its current position, e.g. Y-translated, in the example.

To get rotation and scale after applying them is impossible, as far as I know, unless you have a reference object, but that should have been planned in advance.